About Roof Overlay Work (Cover Method)

Table of Contents

• Roof Overlay (Cover Method)
• Construction Process

Here, we provide information about our roof overlay method. Please take a moment to read through it for your reference!

Roof Overlay (Cover Method)

The roof overlay method involves leaving the existing roof largely intact and placing a new roof on top of it.
Literally, it is a method of covering a roof with another roof. Therefore, the roof becomes double-layered. Since the roof is laid over the existing one, it is also referred to as “overlapping roofing.”

Advantages of the Overlay Method

Since a “new roof” is placed over the “existing roof,” there is almost no need for demolition work, meaning very little waste material is generated.
This is the biggest feature and leads to various advantages.

The only parts that require demolition and waste disposal are typically the ridge cap, making it more cost-effective compared to complete roof replacement.
In 2004, regulations regarding the concentration of asbestos in raw materials were changed (for more details, please visit the Ministry of Health, Labour and Welfare website).
Some building materials used in constructions prior to 2004 contain asbestos. Asbestos-containing materials are difficult to demolish due to their high environmental impact, resulting in high costs for both demolition and waste disposal. The overlay method, which generates almost no waste, is ideal for such roofs.

Some may wonder, “Is it safe to live in a building that uses asbestos-containing materials?” Rest assured, as long as there is no destruction or crushing, it will not disperse into the air.
If you are unsure about the type of roof on your home, please feel free to consult us.

Additionally, the construction can be completed in a shorter timeframe compared to painting or complete replacement. A shorter construction period means lower labor costs, which in turn reduces overall expenses.
The psychological anxiety of having to live in an unusual environment is also minimized.
When scaffolding is erected, it can be inconvenient to enter and exit, and windows may be difficult to open. Being able to return to normal life in a short period is a significant advantage.

Unfortunately, there are also disadvantages to the Overlay Method.

Tile roofs are not suitable for the overlay method.

For typical residential roofs, metal and slate (color best, colonial) are suitable for the overlay method, but tile roofs are not. Additionally, installing solar panels becomes difficult. While it is not impossible to work with tile roofs or solar panels, it is usually more cost-effective and easier to handle with other types of construction.
Please feel free to contact us for details on which roofs are suitable or not suitable for the overlay method.

Depending on the condition of the roof, it may not be possible to carry out the work.

If the underlying structure of the roof is deteriorated, it must be repaired before proceeding. If the overlay method is applied without repairs, it will lead to neglect of the underlying issues, making it impossible to use the overlay method in such situations.

Construction Process (Roof Overlay Method)

1. Dismantling the Existing Roof Ridge
We will remove the ridge metal that is unnecessary for the overlay method.

2. Installing Roofing (Waterproof Sheet)
We will install a waterproof sheet called asphalt roofing on top of the original roof.

3. Main Construction
We will install the new roofing materials.

4. Installation of the Kanban Board
Once the roofing materials are installed, we will install the kanban board. We recommend using resin kanban boards that are resistant to corrosion.

5. Installation of the Ridge Metal
After the installation of the kanban board is complete, we will proceed with the installation of the ridge metal.

6. Caulking Process
We will perform caulking to prevent moisture from entering through the seams of the metal.

7. Completion of Roof Overlay (Cover Method)

As you can see, the roof overlay (cover method) involves fewer processes compared to a roof replacement project.
This not only shortens the construction period but also offers the advantage of saving on costs such as waste removal!

Helpful information about exterior renovations can be found here!

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